1. Field of the Invention
The present invention relates to the field of equipment for driving a pile member, and more particularly to a hammer and associated equipment for driving a pile member from an offshore installation, and to a method for producing a reciprocating impact load against a submersed pile member, as well as to a method of field assembly and disassembly of a hammer.
In the pile driving equipment field, there is always a need for equipment that can withstand high impact shock loads for long periods of time with minimal maintenance. It is also desirable that such equipment be easily and quickly disassembled and reassembled in the field for maintenance or replacement of component parts. The present invention fulfills such needs.
In offshore pile-driving equipment, there is always a need for hammers and associated equipment which can be quickly and easily installed and removed from an offshore installation. There is also always a need for pile-driving hammers which can efficiently operate when submersed in deep water, i.e., at depths of several thousand feet, and still develop a high rated striking force. The present invention also fulfills these needs.
2. Description of the Prior Art
The pile-driving hammer of the present invention is similar to that disclosed in the U.S. Pat. No. 3,927,722, for a pile-driving hammer, issued on Dec. 23, 1975 to myself, Leonard L. Frederick. Both utilize a stationary main valve means for the working fluid, which is disposed within a reciprocating ram structure on a stem member which is in sealing, sliding contact with the reciprocating ram structure. Both have top and bottom compression chamber means for respectively decelerating the ram structure at the end of its loading stroke, and preloading an anvil structure just before it is struck by the ram structure. Both have means for enveloping the end of the pile member in pressurized air to assure that the driving impact against the pile member takes place in air, rather than in water.
The hammer described herein can be used for any application for which the hammer described in U.S. Pat. No. 3,927,722 is used; however, the reverse of this statement of interchangeability does not apply, since the hammer disclosed herein is capable of efficiently operating at much greater depths than the hammer disclosed in U.S. Pat. No. 3,972,722.
The hammer disclosed in U.S. Pat. No. 3,927,722 uses compressed air as its working fluid, and thus is limited as to operating depth to a few hundred feet, whereas the hammer disclosed herein uses pressurized liquid as its working fluid, which is not only over twice as efficient as air, but can be operated at higher pressures, thus allowing the use of a smaller hammer and working fluid supply lines than the referenced air operated hammer for the same striking force, and efficient operation in a range of water depths up to 4000 feet.
Also, the quantity of high pressure air required to prevent entrance of water into the hammer disclosed herein is minimized because it is not mixed with the working fluid, as is the case with the referenced air operated hammer.
The hammer disclosed herein uses a single, push-rod sliding valve means to control the position of the main valve, whereas the referenced hammer requires two cam-operated ball valves. Also, the main valve for the working fluid in the hammer disclosed herein is simpler than the equivalent valve of the referenced hammer, since it only controls the admittance and exhaust of working liquid to the firing chamber for the ram structure, rather than to both the loading and firing chambers for the ram structure, as does the referenced hammer. Also, the further valve means of the referenced hammer, which connect the loading chamber with the top compression chamber, is not required in the hammer disclosed herein.
Also, a unique packing gland for sealing the top end of the ram structure, which is secured to the ram structure by a locking taper joint, and easily assembled and disassembled in the field, is disclosed herein. whereas the referenced known hammer uses conventional closure means.